254 
RESEARCHES ON EMERALDS AND BERYLS* 
Part I, ON THE COLOURING-MATTER OF THE EMERALD. 
PROM the time of Vauquelin’s analyses, the colour of the 
j emerald was always regarded as due to the presence of 
oxide of chromium, until the publication of the memoir of 
Lewy, who ascertained that emeralds contained that element, and 
concluded that the colour was due to the presence of some 
organic substance. Lewy also affirmed that the deepest tinted 
emeralds contained the most carbon. Wohler and Rose, on the 
other hand, having exposed emeralds to a temperature equal to 
the fusing-point of copper for one hour, without their losing 
colour, and also having fused colourless glass with minute 
quantities of oxide of chromium and obtained a fine green 
glass, considered chromium and not organic matter to be the 
cause of the colour, 
Boussingault, in the course of an investigation of the ‘‘ mo- 
rallons,” arrived at the same conclusion as Wohler and Rose ; 
and although admitting them to contain carbon, denied that it 
was the cause of their colour, inasmuch as they endured heating 
to redness for one hour without loss of colour. This result has 
been confirmed by Hofmeister. I have carefully repeated and 
extended these experiments. The emeralds employed were 
canutillos from Santa Fe de Bogota. Their specific gravity was 
2°69. 
Oke of the above emeralds was exposed for three hours in a 
platinum crucible to a bright reddish-yellow heat. At the end 
of the operation it was rendered opaque on the edges, but the 
green colour was not destroyed. This experiment completely 
confirms those of Wéohler and Rose and Hofmeister. The 
power of the colouring-matter to resist a red heat having made 
me inclined to disconnect the question of the colour from that of 
the presence of carbon, I made experiments to determine 
whether beryls contained that element, and, if so, to what 
amount. ‘The experiments given further on, were made at this 
stage of the inquiry, and the result showed that the beryl ana- 
lysedt contained the same amount of carbon as Lewy’s emerald. 
Although demonstration had been obtained of the presence of 
carbon in the beryl A, it was still possible that it might have been 
derived from the decomposition ofa carbonate. To settle this ques- 
tion, an apparatus was so arranged that the beryl could be treated 
with sulphuric and chromic acids successively. It was found 
that no carbonic anhydride was liberated by sulphuric acid, but 
the addition of chromic acid caused it to appear immediately. 
The numerous precautions taken are fully described in the origi- 
nal paper. 
Strictly comparative experiments were then made upon minute 
quantities of charcoal and graphite, the results indicating the 
carbon contained in the beryl A to be in a condition which is 
more slowly attacked than either charcoal or graphite, and it is 
probably in the form of diamond, as has been shown to occur 
with the carbon contained in artificially crystallised boron, 
The presence of carbon in beryls does not appear to be in- 
variable. After repeated experiments upon another large beryl 
from Haddam County, North America, I was unable to satisfy 
myself that it contained carbon. 
The next point I wished to ascertain was the’ relation borne 
by the quantity of carbon in the beryl A to that in the emerald. 
For this purpose I employed a similar apparatus to that used by 
Dumas in his researches on the atomic weight of carbon pre- 
viously alluded to. The following percentages were obtained :— 
Beryl A. Lewy. 
SS Emerald. Emerald 
I, Hig (mean). 
Carbon anhydrid o°31 0°31 0°26 0°28 
Wrater 0. es 1°35 1°73 1°20 1°89 
Il.—ON THE EFFECTS OF FUSION UPON EMERALDS AND 
BERYLS. 
On the Effects of Fusion upon Opaque Beryls—In order to 
study the effects of fusion upon beryls or emeralds, I found it 
necessary to use the oxyhydrogen blowpipe. My first experi- 
ments were made upon the beryl A; it weighed 62°54 grms., 
and its density was 2°65. 
The phenomena observed on submitting a fragment of beryl 
to the action of the flame are very beautiful. Having so ad- 
justed the flame that the beryl fuses tranquilly, and is yet at the 
exact point of maximum heat (if the substance is not too large 
* Abstract of paper read before the Royal Society, June 19. By Greville 
Williams, F.R.S. 
+ As this beryl will be repeatedly alluded to in this paper, and especially 
in the second part, I shall, for convenience of reference, call it *‘ beryl A.” 
It was found in Ireland. 
NATURE 
[Fuly 24, 1873 
for the apparatus), it no longer lies as a shapeless mass on the 
car bon support, but gathers together, rises up, and forms a per- 
fect bead—round, clear, and trilliant. To obtain the adjust. 
ment of position necessary for this result, it is indispensable to 
wear very dar k glasses, so dark, indeed, that objects can scarcely 
be discerned through them in broad daylight. Without this 
precaution, the minute details of the globule cannot be observed. 
The heat and glare would also seriously affect the sight. If all 
is working properly, the bead should Be quite mobile ; and ad- 
vantage of this must be taken to keep it incessantly rolling, and 
yet not remove it from the point where it gives out the most 
brilliant light. By this means the whole globule is rendered 
transparent. If, on the other hand, it is allowed to remain with- 
out motion on the carbon (unless the globule be very minute), it 
will be found, when cold, to have a white opaque base, passing 
into the centre of the bead in a conical form, and entirely de- 
stroying its beauty. 
The globules thus obtained from the beryl A were clear and 
colourless, but generally contained a few minute air-globules and 
strize, which become obvious under the lens. Towards the end 
of this part of the investigation I succeeded in almost entirely 
avoiding these defects ; but I have been compelled for a time to 
abandon experiments in this direction in consequence of the 
strain thrown upon the eyes. 
When chromic oxide is added to the beads, and they are again 
carefully fused, they acquire a fine green colour ; the tint is, 
however, inferior to that of the emerald. The green beads may, 
by anintense and prolonged heat, be rendered colourless. With 
cobalt oxide the beads afford beautiful blue glasses of any de- 
sired shade ; and in all cases the results are the same as with the 
artificial mixture of beryl ingredients to be described further on. 
The effect of fusion upon the beryl is to lessen the hardness 
and lower the specific gravity. The globules may be scratched 
by quartz. The specific gravity was found to be 2°41. 
The beryl, therefore, lost nine per cent. of its density in pass- 
ing from the crystalline to the vitreous state. 
I was desirous of carefully comparing this loss of density under- 
gone by beryls with that of rock crystal fused under the same 
circumstances. I have repeated with great care the determina- 
tion of the specific gravity of rock-crystal, both before and after 
fusion. Before fusion it was 2°65, and afterwards, 2°19. 
Rock-crystal loses, therefore, no less than seventeen per cent. 
of its specific gravity on passing from the crystalline to the 
amorphous state, or about half a per cent. less than is undergone 
by garnets, according to the observations of Magnus; whereas 
the beryl A only lost nine per cent., or little more than half as 
much. ; 
On the Lffects of Fusion upon Emeralds,—On heating alone 
before the oxyhydrogen blowpipe, emeralds bear a bright red 
heat without losing their colour; and at a heat which causes 
incipient fusion, the edges turn colourless and opaque, while the 
centre remains green. After fusion for a short time they yield 
an opalescent greenish glass, which, kept for a long time at the 
maximum temperature of the blowpipe, becomes quite trans- 
parent and almost colourless. The addition of chromic oxide 
causes the bead to become of a dull green colour, which is not 
improved by moderate heating. The fact that emeralds endure 
a temperature capable of fusing the edges, without the centre 
losing colour, appears conclusive against the idea of the colouring- 
matter being organic. The beads produced by the fusion of 
emeralds resemble those formed in the same manner from beryls ; 
the phenomena during the fusion are also nearly alike ; but it 
takes longer and a higher temperature to produce a colourless 
transparent bead with emeralds than with colourless beryls. The 
beads can be scratched by quartz, and the density is reduced to 
2°40, The density of fused emeralds is therefore almost exactly 
the same as the globules obtained in a similar manner from the 
beryl A. 
On. the. Effects of Fusion upon an Artificial Mixture of Beryl 
Ingredients.—Being desirous of trying the effects of fusion upon 
an artificial mixture of the same composition as that of a beryl, 
I made a series of careful analyses of the beryl A, Even my 
earlier analyses enabled me to obtain a sufficiently close approxi- 
mation to the compositions of the beryl A. The following were 
the proportions used ;— 
Silica’ (eyemedeas oa. eGR 
Aluminaege ere 29 20% 18°5 
Glucina iiiees -. te ciety 14’0 
100°9 
v 
